Method of fabricating contacts for fluorescent starter switches



H. M. BURT ET AL 2,434,905

METHOD OF FABRICATING CONTACTS FOR FLUORESCENT STARTER SWITCHES Jan. 27,.1948.

' Filed July 8, 1944 4 Sheets-Sheet l B RT w 8 4 1 2f A \P, if L; Lr LP.1 AM .n 5 0g 7 2 8N Q5 6: 5 @W m@ w a m h 2: m 02 147' OQNEY I Q3 i BJan. 27, 1948. H. M. BURT ET AL 2,434,905

METHOD OF FABRICATING CONTACTS FOR FLUORESCENT STARTER SWII'CHES FiledJuly 8, 1944 4 Sheets-Sheet 2 Q M mi) INVE RS HHRRY M- u 7 v G H. BU

ATTORNEY I Jan. 27, 1948. H. BURT ET AL METHOD OF FABRIGATING CONTACTSFOR FLUORESCENT STARTER SWITCHES 7 Filed July 8, 1944 4 Sheets-Sheet 3 VI I] v A ltlr'ljh N 1 \v a O VENTOR. v (\I Han-Ry M B vr }Q q 5' v GW#80" I I 4 v J I A TZOPNFY Jan. 27, 1948, H. M. BURT Em, I 2,434,905

METHOD OF FABRICATING CONTACTS FOR FLUORESCENT S1'ARTER SWITCHES FiledJuly 8, 1944 4 Sheets-Sheet 4 0 L9 o g (D O q 3: 0 3* g 3 Q H W k 5AAJTZOQNEY Patented Jan. 27, 1948 UNITED STATES ATENT OFFICE METHOD OFFABRICATING CONTACTS FOR FLUORESCENT STARTER SWITCHES Harry M. Burt,Narragansett, and Guy H. Burt, Edgewood, 1.

Claims.

This invention relates to a method of fabricating electrical contactsfor fluorescent starter. More particularly, the invention is concernedwith contacts of the character described which are fabricated from sheetmetal stock, the term sheet metal being used herein to include flat,bent, curved, tubular and variously shaped lengths and pieces of thinself-form-maintaining material.

Heretofore, contacts for starter switches have been fabricatedconventionally, by turning down solid metal stock, for example, byremoving metal from a section of a rod in a screw machine, to impart thedesired shape thereto. This practice has been assiduously followed due;principally, to the peculiar shape of most starter switch contacts. Suchshape consists of (1) a cylindrical shank long enough to extend throughthe base of a starter switch socket, (2) a cylindrical extension on oneend of the shank of smaller diameter than the shank and long enough toproject through a starter switch base with its free end upset intoengagement therewith, and (3) a pair of transverse spaced flanges at theother end of the shank to couple with a resilient blade in the socketand secure the starter switch against undesired displacement. The flangeintermediate the ends of the contact has been the principal reasonheretofore for making said contacts by machining. In some contacts, anaxial bore is provided into which an electric lead from the interior ofthe switch may be inserted and secured by the introduction of fusibleelectrically conductive material, e. g., solder, from the outside of theswitch. In solid contacts, the tubular extension is recessed tofacilitate upsetting and making an electric connection to the starterswitch.

The formation of these contacts by metal removing operations has beenattended by substantial expense because much of the solid stock had tobe removed when forming a contact. This entailed the purchase of metalwhich eventually had to be removed as scrap in expensive machiningoperations.

It is an object of the present. invention to provide a method formanufacturing an intermediately flanged contact such as described inwhich the majorportion of the scrap, if any, is removed, before thecontact is formed, by a simple operation, such as shearing, to provide awork blank which can be fabricated into the desired shape with thesubsequent removal of little or no scrap. Another object of theinvention is to provide tact of the character described on aneconomical, rapid, mass-production basis.

Other objects of this invention will in part be obvious and in parthereinafter pointed out.

The invention accordingly consists in the features of construction,combinations of elements, arrangement of parts and performance ofoperations which will be exemplified in the constructions and methodshereinafter described, and of which the scope of application will beindicated in the appended claims.

In the accompanying drawings, in which are shown various possibleembodiments of this invention and wherein like numbers refer to likeparts, I

Fig. 1 is a bottom plan view of a starter switch socket having disposedtherein a starter switch with contacts made in accordance with ourinvention;

Fig. 2 is a sectional view taken substantially along the line 2-2 ofFig. 1;

Fig. 3 is a bottom plan view of the switch alone;

Fig. 4 is an enlarged sectional view of the novel switch contact, takensubstantially along the line 4-4 of Fig. 3;

Fig. 5 is a side elevational View in partial section of an eyeletmachine tooled up to make said contact; I

Fig. 6 is a plan View of the bed of the machine; Figs. 7 and, 8 areenlarged fragmentary sectional views of the blanking dies at successivestages of their operation;

Figs. 9 and 10 are similar views of the cup forming dies;

Figs. 11 and 12 are similar views of the deep drawing dies;

Figs. 13 and 14 are similar views of the twostep forming dies;

7 Figs. 15 and 16 are similar views of the threestep forming dies;

Figs. 17 and 18 are similar views of the intermediate flange formingdies;

Figs. 19 and 20 are similar views of the top flange forming dies;

Figs. 21 and 22 are similar views of the piercing dies; 4

Fig. 23 is a perspective view of a fully formed sheet metal contact madein accordance with our invention; and

Fig. 24 is a view similar to Fig. 4 of a modified form of sheet metalcontact likewise made in accordance with. theinvention and in which theonly flange is one intermediate the ends of the contact.

a method for manufacturing a sheet metal con- In g n al. we carry outthe stated objects 01 the invention by first forming a sheet metal tubein any conventional manner, for example, by cupping and deep drawing,extrusion, or any well known tube forming method. A tubular element, orportion of the tube having a length corresponding to that of the tubularelement, is then operated upon to impart thereto a shape consisting of aplurality of integrally connected coaxial tubular steps of differentdiameters, that is, in each tubular element at least two tubular stepsof uniform diameter are provided, adjacent steps being of difierentdiameters. If three steps are employed, the slenderest step may have alength and diameter corresponding to the tubular extension (2) which isused to secure the contact to a starter switch. breadth may have adiameter and length the same as that of the hollow tubular shank (I) inthe finished contact. The tubular step of greatest diameter may have alength such that when further operated upon to provide the neces-- saryflange or flanges, the contact will be of the right overall length. Thedifierence in diameters between the second and third steps provides ashoulder intermediate thetwo steps which enables us to form theintermediate flange in a, novel manner.

After the tubular element or portion consisting of a plurality oftubular steps is formed, one of the steps, and preferably the larger oftwo adjacent steps, is axially compressed against an abutment member atthe shoulder between said two steps. During this compression, theportion of the tubular element spaced from the shoulder is laterally,externally supported, leaving only a short portion, no greater than thediameter of the step, adjoining the shoulder laterally unsupported. Theoverall length of the laterally supported and unsupported portions ofthe compressed step is so proportioned relative to the diameter of saidstep, that this step will act as a pure compression member rather thanas a column under axial compression and will tend to bulge outwardlyrather than buckle, particularly when partially laterally supported asdescribed. We prefer for this ratio of length to diameter of thecompressed step not to exceed 3 and best results are obtained when saidratio does not exceed 1.5. According to the invention, the bulgingmovement of the laterally unsupported portion of said step is confinedand directed to force said portion to assume the desired configurationof a double-walled intermediate flange.

While the intermediate flange is being formed, the free end of thecompressed step may be curled over and subsequently, if desired, saidstep may again be compressed, this time without any external lateralsupport whatsoever, the dies employed in compression being so shaped asto force the curled portion outwardly to provide a doublewalled endflange spaced from, the aforesaid intermediate flange.

Finally, the bottom of the cup which is integral with the slenderesttubular step is pierced, so that a lead from the starter switch may beinserted therethrough; also, so that this opened end may be spun over orriveted onto a supporting member, e. g., a fibre disc or plastic can.

Referring now to the drawings, and more particularly to Figs. 1 through4, we have there shown a sheet metal contact 30 made in accordance withthe invention. Said contact is furnished as a part of a starter switch32 which may be of .any conventional construction and is housed in asuitable container, such as a plastic can or the The step ofintermediate light sheet metal can 34 whose ears 36 are inturned tosecure the can to an insulating disc 38. The can houses a suitableswitch, not shown, which may be adapted to close and open a startingcircuit for a fluorescent electric discharge lamp. Said switch isconnected in the starting circuit by a pair of lead wires 40.

The contact 30 is made, from light, electrically conductive sheet metal,for example 22 gauge brass, and is generally tubular in shape so as toprovide a continuous bore from end to end. The

shank of, the contact consists of a seamless tubular step 42; to whichthere is integrally connected another seamless tubular step 44 ofsmaller diameter. This latter step extends through an aperture 4B in thebase of the insulating disc 38 or,

its, plastic. can isemployed, through an aperture in the bottom wallthereof. The step 44 is of suihcient length to permit the free endthereof to extend into the interior of the can 34, where it is, spunover, yeleted or riveted to. form a bead 48. which is clench d ti ht yaga st h i er surface of the disc 38.01. on ner. At t other end of theshank w provide a th'rdseamless tubu, lar step 50 of larger diameterthan the shank 4,2. The tubular step 50 includes two. flanges, oneflange 52 immediately adjacent an end of the shank and the other flange54 spaced from said first flange. Between the two flanges the third step58 has a constricted portion 56 which is of greater diameter than thatof the shank 42. The free end of the third step 50 has a portion 51.which is perpendicular to the longitudinal axis of the contact 30 and aninturned retroverted portion 58 which provides a smooth surface at theexposed end of the contact. After a contact, 30 is secured to a disc 38or plastic can, one of the lead wires 431s inserted therein from theinner surface of the disc 38 or can, this lead wire only extendingpartly through the contact as indicated in Fig. 4 or the lead wire isextended completely therethrough and the protruding portion cut off. Thedisc or can is then inverted to place the flange 54 uppermost and afused electrically conductive material of low mating point, e.,g.,solder 60, is poured into firmly hold the lead wire in place.

A contact of the shape described is adapted to be used in anyconventional present day socket for a fluorescent starter switch such,for example, as the socket 62 shown in Figs. 1 and 2. This socket may beof the type shown and described in Letters Patent No, 2,280,741 issuedAugust 21, 1 942, and consists of side walls, 64 and an intermediatetransv rs p n 66 w ch s rves est e s cket base. Said partition has apair of arcuate concentric keyhole slots 88 formed therein in which thecontacts 3!) are adapted to be received. On the under surface of thebase 66, are a pair of lobster claw contacts 'lil whose spring fingers12 are dap d to resiliently grasp t e c ntacts 38 when they are at thenarrow end of the keyhole slots 68. It will be noted that the fingers 12are so located that they will engage the contacts 39 between the twoflan es 52, 54. This prevents the starter switch from shifting axiallyuntil the same has been rotated out of engagement with the fingers.

The steps for fabricating a sheet metal. contact such as iust describedare shown in Figs. 5 and 7 through 22. First, a circular disc or workblank (Figs. 7 and 8) isblanked out of a sheet metal strip '82 which isfed from a reellnot shown) of such material. This disc is then formedinto a large cup 84 (Fig. 9) of adiarneter greater than that of anyoithe tubular steps later to .beformed.

g. Next, the cup is stripped (Fig. from the cup forming dies. From thisstage the large cup is transferred to a set of drawing dies (Fig. 11)which reduce the diameter and increase the length of the cup 84 toprovide a cup 86 whose diameter is approximately equal to that of thethird or largest tubular step and is, therefore, also approximatelyequal to the diameter of the constricted portion 56 between the twoflanges 52, 54 ultimately to be formed.

The cup 86 is then stripped (Fig. 12) from the drawing dies andintroduced to the two-step forming dies (Fig. 13) at which time theintermediate step 88 is impressed therein, the diameter of this stepbeing approximately equal to thatof the shank 42. The cup-like element98 with the two steps provided therein is stripped (Fig. 14) from thetwo-step forming dies and transferred to the three-step forming dies(Fig. 15) in which the last step 92 is drawn, the diameter of this stepbeing equal to that of the tubular contact extension 44 and the lengththereof being greater than the thickness of the disc 38 or base of theplastic container. The diameter of all the steps may be brought to theircorrect dimensions in the three-step forming dies.

It will be noticed that the step 88 in the element 90 is of such lengththat when the smallest step 92 is subsequently formed at the bottomthereof, the resulting intermediate step 94 and end step 92 are equal tothe lengths of the tubular shank 42 and unspun tubular extension 44,respectively.

Next, the cup comprising three tubular steps is stripped (Fig. 16) fromthe three-step forming dies and shifted to the intermediate flangeforming dies.

It may be mentioned at this point that the preceding operations areconventional per se; that is, it is well known to blank out work pieceswhich are subsequently formed into cups having tubular steps ofdifferent diameters, and it will, therefore, be realized that thetubular element having a plurality of tubular steps of differentdiameters may be formed in accordance with well known practices otherthan those disclosed. For example, more or less than the five stepsillustrated may be used to make the three-step tubular element. Thus,the blank 80 may be out out and the cup 86 drawn in the same operationby a subpress die. Likewise, the three tubular steps all may be formedat once. Alternatively, the drawing and step forming operations may beextended over more than the four steps indicated in order to reduce thestrain to which the sheet metal is subjected in any one operation.However, the actual form imparted by these operations, to wit, at leasttwo tubular steps of diiferent diameters, is of particular importance inaccomplishing the formation of the intermediate flange as will now beseen.

After its fabrication, the three-step cup is fed to intermediate flangeforming dies in which the shoulder 96 between the largest tubular step98- and intermediate tubular step 94 is seated on an abutment member(Fig. 17) which affords lateral support for the intermediate step butnone for the largest step. Said largest step is now subjected to axialcompression and at the same time the upper portion thereof is externallylaterally supported, i. e., the external surfaces of its side walls aresupported. Because of the relative dimensions of the length and diameterof the third step, in the ratio of approximately 1.25:1, said stepaetsas a pure compression member rather than the shoulder 96. This willcause the bulged out of the undeformed portion of the large step 98 neednot be pressed against the shoulder 96'but can be left spaced a slightdistance thereabove.

In such case and with the aid of confining die portions of the propershape, the intermediate flange may be given a truncated conical config-'uration such as shown in Fig. 19, the shoulder 62 being transverse tothe longitudinal axis of the contact and projecting further than theshoulder 96 of the simple three-step cup. The side walls li l of saidflange taper upwardly to provide the shape illustrated rather thanextending perpendicular to the longitudinal axis of the contact as isthe case in the bead I00. It will thus be appreciated that the specificcontour of the intermediate flange can be varied at will and will dependin each instance upon the particular shape desired. It is even possibleto have the shoulder i532 flare upwardly by providing a conical seat forthe shoulder 98 of the requisite negative configuration.

- The essential elements of this stage of our invention are seating anend of one of two adjacent tubular steps of different diameters againstan abutment member and axially compressing said one step while leaving aportion thereof laterally unconfined so as to cause a localized bulge tobe formed at said unconfined portion where a flange is to be located. Inaddition, said bulge is preferably confined and forced into a desiredand predetermined contour.

At thetime the intermediate flange is formed, we may also curl in theupper or free end of the large tubular step 93 to provide an inturnedsingle-walled flange 36 (Fig. 17).

Next, the partially formed contact I08 is stripped (Fig. 18) from theintermediate flange forming dies and transferred to the top flangeforming dies (Fig. 19) where the curled in portion are is retrovertedand the large step 98 subjected to compression without lateralconfinement. This causes the upper part of the said large step to bulgeout, said bulged out portion being directed into the desired shape ofthe double-walled flange 54. This end flange forms at the requiredplace, firstly, because the lower part of the third step 98 isreinforced against bulging by the previously formed bead I00, and,

secondly, since the dies are so shaped as to force the upper portion ofsaid step outwardly. The effect of forming the end flange 54 is toprovide the constricted portion 56 between the two' flanges. The upperflange normally assumes an inverted truncated conical shape, such asthat indicated, with a flat top I89 and tapering side walls He. However,if it is desired to have thefiange 54 in the shape of a fiatdouble-wailedring such as the bead 100 shown in Fig. 1'7, a suitableabutment member may be inserted at the conresilienftlyfdriven through aspring KnOFShdw-n) has; the fihnsei t th ohei hm H4 o the-s p a dsarethe h) I qhhtact ready r sert n in an a e tu e. 4..

an in Ea ing s 8- hi fin shed whieqtii hownih F 3- t i l be. a e ed.hat, h o eg ing oper eti hsper p med p n bula sh et eta Sto areehhhmelreconom th a to time 3 1 hh iih a ount at m teria which ha t be s5 e thath contacts. an ma at m s e ter ee and le s. hpeh e than @9 1: setse? a sm lar-shap hereibieremeds in a ser w machin t; detail. one spe ific armo epar te rwhieh ll-operat n ahi hl safii iiest and some its tm hhe vaid,a, par hi eemprises a multiple p e J20, qfth iy k o n n the t a as aeye e m q.,. i and n des a b 2 h i g eight plnngers (not shown), allcarried above the bed was? rame has o the p nheers s ada ted tc-Qaus thee ormance o a s p t Opera i n up the wo pi e n p er y imessl Qn i Theeri act in its hiiohs stag s. Qh m e from vinegar t P un ah fier slid 5i Q IliI la in ist); fimllllv il g a P ir o Par l de ba l '2 A sh sttion o th m s he V1162? om opera en ior ex m le. b anking sli p n d awistepping or flanging, is performed the bars I re fi ffil 'id fi w t aPai of finger e h 1.2 3. 4 at e blan n stat on.- iT s are nir a y mou td on, he h s and are e i e rg toward each o he y p n s 132- Ea hair ofin er t s-i sh ed s negat ve ohiorm o the xte nto of; the blank o a t yi med .q toqt at he station with hioli they are associated. Suitable meaVine? hown s, provid d to re p o ate the side bars I26 a distance equalto the miforrn pec-2e b ween the adiaoentvlhhga inarertai timedrelationship to the operation of the dies as gillsoonbe more fullyexplained.

As illustrated, the eyelet maoh-ine has seven sta ion denomi at 'A lH-In s? am th bla in stat on A, the cupp n s ation 3 the dra lng station.0, the twostepjorining station the hrees ming s t on h er-- mdi tefi germ s ation E, th to flan e form-m s a ion G hdih ie c ngsta h I{Ihe'blanking operation hereinlieforedescribed,

s ramm d at 'tat eh A. Thi s at on hee blan in dies comp is ng a a v l I7 and 8 nd a p h 3 6 which is recip' b: atesi' i th r t l nge he z iacer the anvil has agroove L38 Iormed therein to rsssi a d guide the int mtten ly t s o l; stripfil whieh isslidably retaihfirl in position .by ao Plate lhel anhing p n h 6 co operates with re iste ed ape 2, 4 11 thecover plate ar i d anvil, respectively, to ents air..- qua; work piecerom th o k trip 82 and dj, o t i upon ar rdeiie ste l blo 43 s nto theed 22 of the ine hi eh D t Qh 1336 is pun h .361125 the c v pla e en the.h Plhh a h itd w h? he when 13,6 g, t pm 1 a n i c ntaot with until thep ir offingers I28, I30 at the thereof. The stock strip 82 is strippfidfrom the wash L fl sh s: t e .20? hi t tr k h tiiii sfer, slide willshift the flat blank 80 from iahehh. p statio B and oe te s d an tespesimf he u hihg d es at s atte s fIAtfstat on 36 555 5. 9 an 10) theb a k s urred, The-dies at h s stat on include a hard.- eped steel ploglI50 having an aperture I52 over wine the plank 80 is centered by thetransfer s de fiaidbl -hh s iQlQd into the e r by a liardened steel cipping pin I54 coaxially dis o ih e beci o i pe t e nd ha n a li iir-szhal 'e than hat Of t ape e r n amount do b e the thic ss of th oc 8be ing gr pped. The-pin I54 depends from a tapered 'plfig 156 which isdriven from its" associated plunger through aspring I58. It will beapparent that, when't Plun r moves t u and n down, the blank 80 will beresiliently pressed into s a es; he cup 4- "H e relative timing of thetransfer slide and sepond pl nger is such that the first pair of fingersI28, I30 associated with station A will hold the n n blank 80 atrfithtion B until said blank is Q 53!? y the d c ndin pin '54- mm dsglosegiient to this, the blank is released Joy the transfer slidewhich; however, does not retract o yeish ht me whims the fi s k iii theh hh hs 'si i eh, po t rs i sa fin ers n ermediate the o sta ions v rdto m t t e operations performed at said stations to be carried outbeiore the article being' worked is grasped by thefihe rs- Ifheou'p' 8 4is stripped from the block I55 by a knoels ont'pin' I which works in theaperture I5 andwhose operation is so timed that it will ior'ce tlregupMupwardly as the pin I54 retracts. L11; is'lals o necessary to employ amechanism to rern'oye' theonp 84; from the pin I54, and to this ehdil ep i whi ping t mb '6 h v qfihtial .c'onical'apert'uie' I64 in which thetapered plng'ilfifi is'seated during the down-stroke of the m 5 Th a h'm leh s n ex e na annu grooye I56 inwliigh thebiinrcated arms I 52} of astripping lever are disposed. Said lever is oper steed byfilflqnventiona l cam firiotshownl which n he ih ih to mo e the f ll wihashbn: the ih blel is s with the ta e ed us I55 hh the h 34 i e h stelei h r d mn am ere t? by the k QQ TPQ Ri l I 5- Then the thimble stops,although the pin continues to rise, her a t ip h 911 9.1 film Pin- 4 ti2331 i5 issthe ed t s graspe b a w d s t a esvefihse s se g to hold thsu a te 1boeehih lysired- .N W the ihimbl i if ahsi trans e sli e advahes ausi er tomo e thww .89 to st i n? w erev hissed with .re ehi t9 theii es at hi i fhel nerative v m for the r in for}: 10. 5 1.91 Preventepwh a sl WW 16mm? of sa d hhhhle so that it is epressed .11 the down:ir h s es 1.5-6-

D ehQlE lessesrat, 11-

A ter the blank fi fhas been seretes and ti h A hlbfiiihtQ when o t etra s er; sl d o g s s i nection with station B. the only differencebetween them being in the shapes of the various forming pins and thematching apertures in the blocks which are set into the bed.

At station C the drawing pin "4 (Figs. 5, 11 and 12) has a smallerdiameter than the cupping pin I54 at station B and the aperture I16 inthe block I78 at station C is correspondingly smaller to provideclearance between the pin and said aperture equal to the thickness ofthe blank stock 82. The transfer fingers I80, I82 at station C havetheir tips contoured to receive the slender cup" formed at this station.The relative timing of the thimble I84, pin I14, and transfer fingersfor said station is the same as that of the like elements at station B.

The two-step forming pin I84 (Figs. 5. 13 and 14) at station D has anupper portion I86 of the same diameter as that of the drawing pin I I4.However, this portion is shorter than said drawing pin and has dependingfrom its lower end a thinner pin I88 which is adapted to form theintermediate tubular portion 88. The aperture I90 in the block I92negatively conforms to the configuration of the pin I84, being slightlylarger to accommodate the thickness of the stock. Due to the d fferencein the diameters of the pin portions I86, I88, the shoulder 96 is formedin the tubular blank 90 intermediate the largest tubular step from whichthe flanges later will be fashioned and the intermediate tubular step88, a portion of which will form the contact shank 42 and a portion ofwhich will be drawn to provide the slenderest tubular step 44 at stationE. Transffer fingers I94, I96 shift the two-step tubular blank fromstation D to the centered position shown in dotted lines (Fig. 16) atstation E, where, as at previous stations, the tubular blank is held bythe transfer fingers until initially engaged by the descending formingpin.

At station E (F gs. 5, 15 and 16) the forming pin I 98 is in threesections200, 202 and 204-f successively smaller diameters in order tofabricate the three-step blank heretofore described.

It may be mentioned at this time that the foregoing mechanisms formaking the three-step tubular blank are described only by way ofillustration and that other well known mechanisms as, for example, arolling mill could be equally well employed.

Transfer fingers 206, 208 shift the three-step blank to station F (Figs.5, 17 and 18) and hold same there in centered position until thesmallest step 92 is engaged by a pressure finger 2I0. The dies atstation F are designed to form the lower flange or head I00 intermediatethe two ends of the contact. Said dies comprise a hardened steel block2I2 set into the bed of the machine and having an aperture 2 I4consisting of a lowerportion 2I5 which is adapted to snugly receive thelower tubular step 92 and an upper portion 2I6 which is adapted tosnugly receive the intermediate tubular portion 94, the shoulder 96between these portions being seated at the base of the upper portion2I6. This construction permits the upper and broadest tubular section 98to wholly protrude from the block 2I2 when the three-piece blank isfully seated in the aperture 2I4 by the pressure finger 2I0. Thereciprocating compression die 2I8 at station Fhas a hollow lower end 220which is adapted to fit around the sides of the upper tubular portion98. The top of the hollow portion is rounded at 222 adjacent the sidewalls thereof to curl in the top of the tubular portion 98 during thedown-stroke of said die until the edges of the aperture at the top ofthe partially formed contact abut against the pressure finger 2I0, asbest shown in Fig. 17. As the curled in portions I06 reach the foregoingposition, the full compressive eifort Of the die is applied to the sidewalls of the upper tubular portion 98. Due to the fact that said tubularportion is only about 1.25 times as long as it is wide, it acts as apure compression member-and tends to bulge outwardly. However, the majorportion of the side walls of said portion are externally laterallysupported by the side walls 224 of the compression die 2I8 which definethe hollow lower portion thereof. This leaves laterally unsupported ashort part of the tubular portion adjacent the shoulder 96; saidunsupported part buckles outwardly near the end of the downstroke of thedie 2I8 to form the double-walled bead'lflfl. I

In Fig. 17 the stroke of the die 2I8 has been illustrated as of suchnature as to force the upper and lower walls of the bead together so asto form a flat ring-like double-walled projecting flange. This stroke,however, may be slightly shorter and the tip of the die 2 I8providedwith a beveledseat, if desired, to impart to the bead I00 thetruncated conical shape illustrated inFigs. 19.throug'h 23.

It will be noted that the pressure finger 2 I 0 is backed by a spring226 weaker than the spring 228 operating the, die 2I8,' so that thepressure finger holds its position as the bead is being formed. Thepressure finger spring is set into a cavity 230 in the upper part of thedie 2I8, The die 2I8 has a cylindrical outer contour and slides freelyin a central bore 232 of a thimble 234 at station F, said thimble beingdriven positively into engagement with the block 2I2 by a cam whichmoves the forked stripper arm carrying the bifurcated fingers 236. Thelower end of said thimble has an enlarged recess 238 to accommodate theperiphery of the flange I00 and'aid in imparting the desired contourthereto by forming the outer portion of the confined space into whichthe bulge is directed.

After the partially formed contact pin I08 has had the intermediateflange I00 formed thereon, it is ejected from the aperture 2I4 byknock-out pin' 240 and grasped by transfer fingers 242, 244

before being stripped from the pressure finger 2 I 0 and die 2I8 by thethimble 234. Said transfer fingers thereupon shift the contact element238 to station G.

At station G (Figs. 5, 19 and 20) the element I08 is centered over anaperture 246 in a hardened steel block 248 set into the bed I 22. Saidaperture has an enlarged upper portion to receive the contact shank 42and a smaller lower portion to receive the smallest tubular step 44, thebead I00 resting upon the upper surface of the block 248. The elementI08 is seated in the aperture 246 by a pressure finger 250' which isslidably mounted in a compression die 252 and urged to outthrustposition by a spring 254. The lower end of said die has a, coaxialannular nib 256 which is adapted to inturn the central curled-in portionI06 and thus provide a smooth external surface on the exposed and of thecontact pin. Said nib is connected by an annular fillet 258 to the fiatbase 260 of the die which. subsequent to the inturning action justmentioned, engages the curled-in portion and compresses the uppertubular step 98 in which the intermediate bead I00 has already beenformed. The presence of this bead restricts to the upper portion of thelarge tubular step 98 the bulging efiect caused'by the 13 bular sheetmetal contact for a fluorescent starter switch, said method includingthe steps of forming two integrally connected tubular sheet metal stepsof different diameters, axially compressing, against the shoulderinterconnecting the steps, the larger step while externally supportingthe side walls of said compressed step except at a circumferential zoneimmediately adjacent and including said shoulder, whereby said wallswill locally bulge out at said zone to form a double-walled flange insaid compressed step, one of whose walls includes said shoulder, curlingin the end of said step remote from said shoulder, and subsequentlyaxially compressing said larger step without laterally confining thesame and while turning the curled in portion and internally supportingsaid turned in portion whereby said end will expand to form a secondflange spaced from the first named flange by an annular groove.

HARRY M. BURT.

GUY H. BURT.

14 REFERENCES CITED The following references are of record in the fileof this patent:

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